1. Technical Field
This invention relates generally to an oil heater and more particularly to an oil heater having both radiantly and convectionally heated sections.
2. History of Related Art
Oil heaters are commonly used for a variety of industrial and commercial applications, such as in chemical process heating, petroleum refining, asphalt heating, and lubrication oil and fuel oil heating. Oil heaters are also used to heat other fluids, such as fluids used in metal heat treating and quenching, space heating, food processing and similar applications.
Heretofore circulating oil heaters have been only partially efficient, frequently emitting exhaust gases having a temperature of 500.degree. F. or above. Also, oil heaters having both radiantly and convectionally heated sections have generally been only limitedly efficient because the radiantly heated section and the convectionally heated section have generally been disposed in separate chambers, each having a shell through which heat can be transferred to the surrounding atmosphere and adding length to the heater package. As a result of the added heat loss, the heating efficiency of the oil heater is reduced.
Other oil heater arrangements may provide limited convection heating as a result of positioning some of the flow conduits in the same chamber with a radiantly heated section. For example, U.S. Pat. No. 4,387,766 issued Jun. 14, 1983 to John H. Miller, and titled HOT OIL HEATER WITH HELICAL COIL AND BAFFLE discloses a single helical coil supported on longitudinally oriented tubes which act as skids to support the helical coil within the heater. Fluid flows through the skids, and arguably the skids could be considered as providing limited heat transfer to the incoming fluid as a result of convection heating. However, the convection heating of the incoming oil provided by the longitudinal tubes is quite limited as a result of the tubes having of a relatively short length and being disposed in a lower portion of the firebox, away from the hot gas stream as it flows toward an exhaust stack.
The present invention is directed to overcoming the problems set forth above. It is desirable to have an oil heater that is both space efficient and is efficient in transferring heat from a heat source to a fluid heated by the oil heater.